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Loans Receivable (Summary of Provision for Credit Losses) (Details) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Provision for credit losses | $ 814.7 | $ 736.2 | $ 481.4
Dealer Loans [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Provision for credit losses | 537.3 | 427.7 | 240.4
Purchased Loans [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Provision for credit losses | 277.4 | 308.5 | 241.0
New Consumer Loan Assignments [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Provision for credit losses | 320.9 | 322.5 | 343.7
New Consumer Loan Assignments [Member] | Dealer Loans [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Provision for credit losses | 191.4 | 146.2 | 154.8
New Consumer Loan Assignments [Member] | Purchased Loans [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Provision for credit losses | 129.5 | 176.3 | 188.9
Forecast Changes [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Provision for credit losses | 493.8 | 413.7 | 137.7
Forecast Changes [Member] | Dealer Loans [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Provision for credit losses | 345.9 | 281.5 | 85.6
Forecast Changes [Member] | Purchased Loans [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Provision for credit losses | $ 147.9 | $ 132.2 | $ 52.1

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